difficulty with reverse rotation chev marine engine ignition timing?

Question

on a twin engine boat, twin chevy 350s, standard rotation engine dials in a timing setting and runs perfectly, cool as a cuke, in all operating conditions. The reverse rotation engine, on the other hand, runs a bit hot and the timing mark on the flywheel show 45 degrees advance when I read it with an advance meter. that is the only setting it runs well at. The standard rotation runs good at 8 degrees advance. i checked timing mark against tdc and it is dead on. any ideas?

Answer 1

I'd check the ignition wires. The firing order is different and it's easy to miss wire the engine. Are you sure that it's in fact running in the right direction? I had one that had been rebuilt, and a standard starter was installed and the engine would start and run, much as you discribe, but it was running backwards. I hope this helps.

Answer 2

the engine as viewed from the fly wheel end should rotate counter clockwise the firing order is not the only thing reversed on these engines the water pump is also reverse rotation. So is the starter the starter drive gear bevel is reversed on both the starter and the fly wheel gear



In these reverse rotation engines Gm used a set of gears instead of a timing chain so the distributor and camshaft rotate in the standard direction. Beacause of this number one cylinder is the same on both engines and this is why Number one spark plug wire is in the same position on both distributor caps.



Oh an easy way to remember this is the move number one to the end of the standard firing order and read backwards

here are the firring orders for you



V8 - 305 V8 - 350 V8 454



Std. Rotation 1-8-4-3-6-5-7-2

Reverse ------ -- 8-4-3-6-5-7-2-1



Reverse Rotation 1-2-7-5-6-3-4-8







Again Number one is in the same position on both distributor caps.



Remember this is a four stroke engine so the timing marks will line up twice once at the top of the compression stroke and once on the top of the exhaust if your not careful you can get the marks 180 degrees out of time



The best way bring the engine to TDC is to pull number one spark plug and rotate the engine in the correct rotation slowly with your finger in the spark plug hole till you feel the compression blowing out of the cylinder

This puts the engine on the compression stroke Rotate the engine slowly till the timing mark is top dead center



If I were working on this engine I would run the firing order and re-time the distributor sounds like your one tooth off



Added comment; the camshaft is what is known as a reverse grind cam you can not use the same firing order as the standard engine 1-8-4-3-6-5-7-2



Edit overhauled my first marine engine in 1965 at a shipyard worked on Chris Craft Crusader Hercules Indmar Chrysler Ford and Continental Standard and reverse rotation engines untill 1992

Answer 3

the engine as considered from the fly wheel end could rotate counter clockwise the firing order isn't the only component reversed on those engines the water pump is likewise opposite rotation. So is the starter the starter force equipment bevel is reversed on the two the starter and the fly wheel equipment In those opposite rotation engines Gm used a collection of gears truly of a timing chain so the distributor and camshaft rotate in the familiar course. Beacause of this quantity one cylinder is an analogous on the two engines and that's why quantity one spark plug cord is in an analogous place on the two distributor caps. Oh an undemanding thank you to submit to in ideas that's the flow quantity one to the top of the familiar firing order and examine backwards listed here are the firring orders for you V8 - 305 V8 - 350 V8 454 Std. Rotation a million-8-4-3-6-5-7-2 opposite ------ -- 8-4-3-6-5-7-2-a million opposite Rotation a million-2-7-5-6-3-4-8 back quantity one is in an analogous place on the two distributor caps. submit to in ideas this is a 4 stroke engine so the timing marks will line up two times as quickly as on the right of the compression stroke and as quickly as on the right of the exhaust in the experience that your no longer careful you will get the marks a hundred and eighty stages out of time the final way deliver the engine to TDC is to tug quantity one spark plug and rotate the engine in the final suited rotation slowly with your finger in the spark plug hollow till you sense the compression blowing out of the cylinder This places the engine on the compression stroke Rotate the engine slowly till the timing mark is appropriate ineffective center If I have been working in this engine i might run the firing order and re-time the distributor looks like your one the teeth off added remark; the camshaft is what's many times a opposite grind cam you could't use an analogous firing order because of the fact the familiar engine a million-8-4-3-6-5-7-2 Edit overhauled my first marine engine in 1965 at a shipyard labored on Chris Craft Crusader Hercules Indmar Chrysler Ford and Continental familiar and opposite rotation engines untill 1992

Answer 4

Un fortunately we can't draw diagrams in answers so let me try and explain reverse grind. today it is used a little differently than when kilo rebuilt his first engine.



Picture a standard rotation cam shaft with the gear on the front of the cam. now turn it around and put the gear or sprocket on what was the rear of the camshaft, if you can picture it, what was previously the # 8 lobes are now in the # 1 cylinder position and so on Hence the reverse firing order.



Think in terms of which pistons the CrankShaft brings to top dead center if roatated clockwise and then counterclockwise

with number one always being the same piston

Answer 5

If the heating is the only problem, I would suspect it is a coolant flow problem, rather than a timing issue. Take your boat to a good marine shop, have the engine flushed and the heat exchangers inspected. The volume of coolant flow is vital to the proper operation of unit. Also check that the temp guages are accurate. If these are electric, one oxidized connection can cause the readings to be erratic.

Answer 6

Recheck wiring to plugs,I never could remember the reverse order so knowing that the distributor goes clockwise, I would just wire it counter clockwise as 18436572. Make sure you are on #1 firing order. Remove point plate and check advance springs for busted,rusted,stretched out, replace with new for that model engine.

Answer 7

LOWER UNIT ADJUSTMENT